Pressure demand breathing oxygen mask with built-in regulator



June 30, 1959 H. w. SEELER 2,892,456

PRESSURE DEMAND BREATHING OXYGEN MASK WITH BUILT-IN REGULATOR Filed April 21, 1958 2 Sheets-Sheet l INVENTOR. #emer m sea axe June 30, 1959 H. w. SEELER 2,892,456

PRESSURE DEMAND BREATHING OXYGEN MASK WITH BUILT-IN REGULATOR Filed April 21, 1958 2 Sheets-Sheet 2 oxrce/v m/u'r EXHHZfD ,I/E OUT INVENTOR. l/EA/EY W. $6161 1? a 41 a) ,qrr glaxs United States Patent PRESSURE DEMAND BREATHING OXYGEN MASK WITH BUILT-IN REGULATOR Henry W. Seeler, Dayton, Ohio, assignor to the United States of America as represented by the Secretary of the Air Force Application April 21, 1958, Serial No. 730,027 Claims. (Cl. 128-142) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

Developments in the field of oxygen breathing equipment for high-altitude flight have clearly indicated the necessity for the use of oxygen masks which can be pressurized above ambient atmospheric pressure at high altitude, giving rise to the so-called pressure breathing. Further, in order to conserve oxygen the supply of oxygen should be in accordance With the demand rather than continuous flow. In the past, regulators capable of supplying oxygen to satisfy the above-noted conditions have generally been mounted directly on the air frame and connected by long hose lines to the oxygen mask. It has been realized that the pressure fluctuations and oscillations in the low-pressure line leading from the regulator have been undesirable. There has been a long-felt need for a pressure breathing oxygen mask with a small compact regulator built into the mask whereby oxygen under a pressure of, for example, seventy pounds per square inch can be led directly into the regulator and reduced in pressure within the mask for breathing to a level of the order of eight inches of Water. In general, all attempts to build an altitude compensated regulator sufficiently small in dimensions and weight to enable it to be attached directly to the oxygen mask have been a failure.

This invention relates to a compact regulator with a built-in inhalation-exhalation valve, the overall dimensions of which are of the order of one inch in diameter and two inches overall length and only a few ounces in weight. With a regulator of this character it can be directly mounted or built into the face mask and is an adequate solution to the problems heretofore encountered in this field.

The invention briefly consists of a small cylindrical symmetrical casing which is mounted on the front wall of an oxygen mask of the pressure breathing type which is held to the wearers face by a known type of harness. The cylindrical casing is provided with an open end which communicates directly with the interior of the mask, and adjacent its open end there is provided a pressure balanced inhalation and exhalation valve controlling the flow of oxygen to the mask and the exhalation of air therefrom. Above the combined inhalation and exhalation valve there is provided a novel pressure reducing regulator which includes a main valve controlling the flow from the oxygen inlet to a demand chamber positioned immediately above the inhalation valve. The main valve is servo operated by a pressure-responsive motor means, which in turn is pilot controlled, the motor means being actuated by oxygen under inlet pressure and the discharge therefrom being led into the demand chamber. The pilot valve is operated by a diaphragm responsive to the difference pressure in between the demand pressure and the ambient atmosphere. In order to provide altitude compensation the regulator is provided with a very small aneroid which acts against the diaphragm controlling the pilot valve. In order to overcome the obstacle of requiring a large aneroid to overcome the breathing mask pressure the diaphragm controlling the pilot valve engages an annular stop which greatly reduces the effective portion of the diaphragm under such conditions. Further the aneroid transmits its force through a pair of parallel springs of different stiffness with a heavy spring coming into action when the area of the effective area of the diaphragm is reduced. This arrangement makes it possible to use a Very small aneroid and makes the small overall dimensions of the regulator possible. The regulator is also provided with a means for directly manually actuating the pilot valve in the event of any regulator failure. The mask is also provided with an air dilution valve, in one form of which inlet oxygen pressure is employed to relieve a flow restriction, but in the event of complete failure of oxygen pressure the restriction becomes elfective so that a clear warning is present when attempting to breathe in the ambient atmosphere through the diluter valve and indicating that emergency measures must be taken immediately.

While the above is a generalized description of an oxygen mask and regulator as constructed in accordance with the invention, more complete details thereof will be had by reference to the description hereinafter given and to the appended drawings, in which Fig. 1 is a side view, partly in section, of an oxygen mask and regulator construction in accordance with the invention;

Fig. 2 is a side elevation of a mask similar to Fig. 1 taken from the opposite side of the mask and differing from Fig. 1 in the form of diluter valve;

Fig. 3 is a view of the forward portion of the mask taken on line 3-3 of Fig. 1;

Fig. 4 is a longitudinal sectional View, in a scale three times full size, of the regulator illustrated in Figs. 1 and 2;

Fig. 5 is a cross sectional view of a conventional air dilution valve such as shown in Fig. 1; and

Pig. 6 is a view, in cross section, of an improved air dilution valve employed with the mask shown in Fig. 2.

Referring now to Fig. 1, the reference numeral 1 generally indicates a molded rubber mask adapted to fit over the oral-nasal portions of the wearers face and to enclose the same in a pressure tight relation. The mask is adapted to be held to the wearers face by means of straps 2. The general configuration of the mask and harness are the same as that disclosed in my copending application Serial No. 677,167, filed August 8, 1957, for Self Oriented Mask Harness Arrangement. The mask is provided with a front wall 3, which is pierced by a central aperture 3 provided with an integral moulded locking ring 5 adapted to cooperate with a corresponding groove 12 formed in the housing of a combined inhalation-exhalation valve and regulator assembly, generally indicated by the reference numeral 15. The mask is provided with a generally tubular shaped portion 7 which extends forwardly from the front Wall 3 of the mask. The tubular extension 7 surrounds and is substantially coextensive with the regulator assembly 15 but is spaced from the wall of the regulator to leave a concentric annular space 8 which extends from the exhalation ports 24 of the regulator assembly substantially the full length of the regulator body and is adapted to discharge exhaled air to the atmosphere. The regulator body absorbs heat from the exhaled air to eliminate problems of freezing in the exhalation ports. The tubular extension 7 is provided with projections 9 adjacent its front portion which engage the regulator body and hold the same in position. (Note Fig. 3.)

As seen in Fig. 3 tubular mask extension 7 is provided with a boss 10 which serves as a support for the regulator body adjacent the oxygen inlet which comprises a hollow tubular bolt 48 forming part of a conventional type banjo fitting 49 to which the high pressure oxygen hose, not shown, is connected. The hollow bolt 43 is threaded into the inlet of the regulator and serves to conduct oxygen at a supply pressure of about seventy pounds per square inch from the aircraft oxygen supply source, not shown. In general the aircrafts oxygen supply may consist of a number of oxygen bottles carrying oxygen at a pressure of two thousand pounds per square inch and which pass oxygen into a delivery line provided with line regulator adapted to reduce the oxygen pressure to a line delivery pressure of seventy pounds per square inch. The present regulator may also be connected directly into a liquid oxygen generator of a conventional type which delivers oxygen at a pressure of approximately seventy pounds per square inch.

The Regulator The novel regulator in accordance with this invention is shown in a longitudinal sectional view in Fig. 4-. Referring now to this figure, the regulator and valve assembly is generally indicated by the reference numeral and comprises a cylindrical casing made in three parts, a lower part 16 which contains the inhalation and exhala tion valve, a central cylindrical part 17 and an upper cylindrical part 18 closed at its outer end by the transverse wall 19. The housing parts 16 and 18 are suitably internally bored and threaded to screw on to threaded extensions of the central housing section 17. The details of the threaded joints are not shown for the sake of clarity in the general assembly shown in Fig. 4. The regulator shown inFig. 4 is approximately three times full size and not all of the parts are shown in true scale for the purpose of clarity. The lower casing portion 16 is provided with an annular attachment groove 12 previously mentioned with respect to the description in Fig. 1. This lower casing section 16 is also provided with a central bore 20 which at its lower end communicates directly as an outlet to the interior of the mask 1, Fi s. 1 and 2. The bore 20 terminates at its upper end in a sharp-edged annular valve seat 22 which partly masks radial exhalation ports 24 also shown in Fig. 1 through which exhaled air is led out from the mask interior. The valve seat 22 cooperates with a disc type exhalation valve 25, which when seated prevents the leakage of air from the mask interior to the atmosphere. The disc valve 25 is provided with a hollow tubular extension 26 on each side thereof which is provided at its lower end with radial spider arms 27 which serve as a mounting for the central stem 28 of a conventional thin rubber flapper type inhalation valve 30, the edges of which cooperate with the lower periphery of the tubular extension 26 to form a valve seat. During inhalation the thin edges of the inhalation valve are pulled laterally outward to permit a free communication between the interior of the tubular extension 26 and the outlet 20. The spider 27 also serves as a seat for the lower end of a light control spring 31 which normally causes the exhalation valve disc 25 to engage its valve seat 22. A cylindrical sleeve 32 is press fitted into the tubular extension 26 and serves to clamp the inner end 33 of a flexible iubberized fabric seal 34 which is provided with an annular corrugation 35 which serves to pressure balance the exhalation valve disk 25 in the same manner as disclosed in my copending application Serial No. 549,892, filed November 29, 1955, now Patent Number 2,820,469, entitled Combined Compensated Inhalation Exhalation Valve for Pressure Breathing Mask, the pressure compensation features of which form 110 part of the present invention. The diaphragm 34, in addition to its pressure compensating functions, serves to seal off the exhalation ports 24 from the space above the diaphragm. The outer periphery of the diaphragm 34 is provided with an enlarged bead 36 which is securely clamped between the housing sections 16 and 17 when the same are assembled.

The bottom portion of the central housing section 17 is suitably recessed and is provided with a transverse wall 37. The bottom wall 37 is provided with an upwardly directed tubular extension 38 which is rounded at its top to form an annular valve seat 39. The space inclosed from the valve seat 39 downward beneath the wall 37 and the space inclosed by the tubular extension 26 of the exhalation valve 25 are also generally indicated as a chamber 48 which hereinafter will be referred to as a demand chamber, since it is from this space that oxygen is withdrawn into the mask through the inhalation valve 30 in accordance with the demand of the user.

The central housing section 17 is provided with a bore 42 concentric with the tubular extension 38, and this bore is closed on its upper side by means of a flexible rubber diaphragm 43 which is adapted to engage the valve seat 39 and form the main pressure control valve of the regulator. The annular space beneath the diaphragm 43 is generally indicated by the reference numeral 45 and forms the high-pressure oxygen inlet chamber. The central portion of the diaphragm 43 is provided on its upper side with a metal disc 44, against which a control spring 46 acts to normally push the valve portion of the diaphragm 43 into engagement with the valve seat 39 and to obstruct any flow of oxygen into the demand chamber 40. A passage 47 serves as the oxygen inlet to chamber 45 and is threaded to receive the conduit 48 Fig. 3. The upper portion of the housing section 17, forms a control chamber generally indicated by reference numeral 50 and formed by an enlarged counterbore 51 concentric with the bore 42, into which is pressed an inverted cup-shaped closure 52 which also serves to secure the outer periphery of the diaphragm 43. The closure 52 also serves as a seat for the upper end of the valve control spring 46. The closure member 52 is sealed in the bore 51 by means of a conventional rubber O-ring seal 53 and below the seal is reduced in diameter to form an annular passage 54 which communicates with the interior of the chamber 50 by means of a small bleed passage 55 and the annular passage 54 is also connected to the oxygen inlet passage 47 by means of a small passage 56 so that oxygen under inlet pressure can flow upward through the passage 56 into the annular passage 54 and through the restricted passage 55 into the chamber 50, thus applying inlet oxygen pressure above the valve diaphragm 43 so that the pressure on both sides of the diaphragm will be equalized when the valve is seated.

The upper wall of the closure 52 is provided with a central flow passage 57 which cooperates with a small inverted pilot valve 58 normally urged in the closing direction by a conical valve spring 59. The valve 58 when open permits the venting of fluid pressure from the control chamber 50 to an expansible chamber generally designated at 60, in a regulated amount depending upon the amount of valve opening. The passage 57 is considerably larger in cross section than the bleed passage 55 so that when the valve 58 is open pressure within the chamber 50 can be vented at a rate greater than fluid pressure can be supplied through the bleed port 55, and hence a pressure can be maintained in the control chamber 50 which is proportional to the amount of movement of the pilot valve 58.

The upper portion of the housing section 17 is counterbored to form the chamber 60 which is connected with the demand chamber 40 by a drilled passage 61. The chamber 60 is closed on its upper side by means of a flexible rubberized fabric diaphragm 62 which is provided with concentric annular beads 63 and 64, respectively. The upper side of the diaphragm 62 is contacted by means of an annular metal plate 65 shaped to conform with the diaphragm and provided with a central flanged opening 66 which leaves the central portion of the diaphragm 62, including the inner annular head 64, out of engagement with the plate or stop member 65. A metal backup plate 67 on the un'der side of diaphragm 62 contacts the pilot valve 58. A coil spring 68 engages the upper side of the diaphragm 62 in the central aperture 66 of the plate 65 and can apply its full force in a downward direction to the entire diaphragm. The diaphragm 62 on its upper side is also provided with a metal disc 69 against Y which a heavier coil spring 70, concentric with spring 68, is adapted to engage. The bottom coil of the spring 70 is spaced from the plate 69 so that normally the spring 70 will be out of action. The springs 68 and 70 project within the upper housing section 18 which is bored out to form a chamber 75 inclosed at the top by the end wall 19 of the housing section 18. Within the chamber 75 is an aneroid bellows assembly generally indicated at 76 which includes a bottom plate 77 having a central cylindrical recess 78 formed therein which serves as a retainer for the coil spring 70, while coil spring 68 rests in abutting engagement with the bottom of the plate member 77. The aneroid 76 is provided with the usual internal control spring 79 and upper wall member 80 and corrugated thin metal bellows 82 of annular configuration and which is soldered to the plates 77 and 80. The interior of the bellows assembly 76 is premanently evacuated. The uper plate member 80 of the aneroid is provided with a central threaded stem 84 which is screwed into a sleeve 85 which is freely slidable in a boss 86 formed integral with the upper wall member 19 of the housing section 18. The sleeve 85 has a curved plate 87 secured thereto which serves as a knob to manually push the sleeve 85 inward against a return spring 88 which permits the entire bellows assembly 76 to be pushed downward compressing the springs 68 and 70 and transmitting force directly to the pilot valve 58 irrespective of any forces transmitted thereto from the diaphragm 62. The stem 84 of the aneroid assembly 76 is provided at its outer end with a screwdriver slot so that the entire assembly may be rotated and moved axially with respect to the sleeve 85 so as to adjust for the altitude at which the aneroid becomes efiective. The adjustment is fixed by means of a set screw 89 which is tightened down on the stem 84. An annular ring of ports 90 drilled through the end wall 19 of the casing section 18 permit air at atmospheric pressure to enter the aneroid chamber 75 and act on the aneroid 76.

In order to conserve oxygen it is desirable to employ a diluter valve which will open during inspiration to allow air to flow in from exterior of the mask to dilute the oxygen delivered by the regulator and by in part equalizing the pressure dilference between the interior of the mask and the pressure in the demand chamber reducing the flow of oxygen. Such a diluter valve of known type is shown as a general assembly 90 in Fig. 1 and in detail in Fig. 5.

Referring now to Fig. 5 the diluter valve assembly 90 comprises a metal or plastic block or cylinder 92 externally grooved to sealingly fit into the side wall of the oxygen mask 1 (Fig. 1). The block 92 is provided with a central passage 93 communicating at one end with the ambient atmosphere and at its other end through a spider 94 to the interior of the mask. A conventional thin rubber flapper valve 95 centrally supported on the spider 94 is adapted to open inwardly when the pressure within the mask is below atmospheric pressure and permits the flow of diluting air into the mask. When the pressure in the mask during inspiration is always positive the valve 95 remains closed and the aviator breathes pure oxygen. I

Use of a diluter valve such as shown in Figs. 1 and 5 is open to the objection that if there is a failure in the oxygen supply at high altitude the aviator will begin to breathe in pure air through the diluter valve. Breathing the rarefied atmosphere can lead in a matter of a few minutes to serious anoxia and unconsciousness.

In order to give warning to the aviator of the failure of the oxygen supply an improved diluter valve assembly generally indicated by the reference numeral (Fig. 2) is preferred. As shown in detail in Fig. 6 the valve assembly 100 comprises a two part housing, the parts 101 and 102 being threaded together and clamped in the side wall of the oxygen mask 1 (Fig. 2). The chamber 104 of the housing section 102 communicates through a spider 105 with the mask interior. A flapper type diluter valve 106 supported on spider 105 Opens inward when mask pressure is below atmospheric pressure to permit the inflow of diluting air. A partition wall 107 extends between the housing sections and is provided with an annular series of ports 108 therethrough. The ports 108 are adapted to be covered and uncovered by a disc valve plate 109 which controls communication between chamber 104 and the chamber 110 in housing section 101. The chamber 110 communicates at all times with the ambient atmosphere by means of ports 112 in the housing section 101. The valve plate 109 is adapted to be axially shifted by an ex pansible chamber flexible bellows 115 positioned in chamber 110. The bellows 115 is normally inflated by means of oxygen under supply pressure by means of a conduit connected to the oxygen inlet fitting 49, see Fig. 2. So long as oxygen supply pressure is available, the bellows 115 when inflated will move valve 109 to uncover ports 108 and allow a free flow of air through the housing 101102 when the diluted valve 106 opens during inspiration. The diluter valve then operates in normal fashion in the same manner as the valve of Fig. 5. In the event of the failure of oxygen supply pressure due to any cause, the bellows 115 will deflate and valve 109 will cover ports 108 and when the aviator attempts to draw in air through diluter valve 106 the valve 109 will ofier a high restriction to the flow of air through ports 108. This restriction in flow will be immediately apparent to the pilot as a warning that oxygen supply pressure has failed and he should immediately descend to a safe lower altitude.

Operation When a mask and regulator combination in accordance with the invention is placed in operation, the mask is connected by means of a hose line attached to fitting 49, Figs. 2 and 3, which in turn is connected to a regulated oxygen supply at a pressure of approximately seventy pounds per square inch. At low altitudes during inspiration the inter-' ior of the mask 1 will be at subatmospheric pressure so that the inhalation valve 30, Fig. 4, will open allowing oxygen in the demand chamber '40 to flow through the opening 20 of the regulator assembly 15 into the mask interior. As soon as inspiration opens the inhalation valve 30 and oxygen flows from the demand chamber 40 the pressure therein will immediately drop. This pressure drop will be transmitted by means of passage 61 to the chamber 60 beneath the diaphragm 62, lowering the pressure and causing atmospheric pressure acting on the opposite side of the diaphragm to move the diaphragm downward simultaneously moving pilot valve 58 to open the port 57. Since the port 57 is much larger in cross section than the bleed passage 55, oxygen pressure in the control chamber 50 will fall and inlet oxygen pressure in the inlet chamber 45 will then be sufiicient to lift the valve 43 against the resistance of control spring 46 and allow oxygen to flow through the tubular extension 38 into the demand chamber 40. It will be understood that the disc valve diaphragm 43 will just crack open from the valve seat 39 to permit oxygen at 70 pounds per square inch to be reduced in pressure to the order of four inches of water pressure. As soon as the inspiration cycle is complete the inhalation valve 30 will close, due to exhalation pressure exceeding the existing pressure in the demand chamber 40. Oxygen under pressure can then proceed through passage 56 from the inlet 47 into the annular chamber 54 and through the bleed passage 55 and thus build up pressure within the chamber 50. In the meantime reduction in flow from the demand chamber 40 will cause an increase in pressure therein which will be transmitted by means of passage 61 to the diaphragm chamber 60 so that the increased pressure beneath the diaphragm 62 will cause the diaphragm to lift and allow the light valve control spring 59 to restore the pilot valve 58 to the closed position. The valve diaphragm 43 will then seat on the valve seat 39 shutting oil? the flow of oxygen to the demand chamber 40. When the inspiration part of the breathing cycle has stopped and the aviator begins to exhale the increased pressure within the mask will act on the entire area inclosed by the valve seat 22 and will cause the exhalation disk valve 25 to lift from the valve seat and permit exhalation through the exhalation ports 24 into the annular discharge channel 8 of the mask extension 7, Fig. 1. During the inspiration part of the breathing cycle at lower altitudes the reduction in mask pressure below ambient atmospheric pressure will permit the dilution valve 95, Fig. 5, or 106, Fig. 6, to open so that atmospheric air is admitted to the mask to mix with the oxygen and thus lower the requirement for pure oxygen in the manner as heretofore described with respect to the operation of the respective diluter valves. As the aircraft ascends atmospheric pressure in the chamber 75 of the regulator assembly 15, Fig. 4, begins to fall and the control spring 79 in the aneroid assembly 76 will expand the aneroid and transmit an increasing force by means of soft spring 68 to the diaphragm 62. This force will eventually reach a level such that the pilot valve 58 will be open in small amounts and allow the pressure in the demand chamber to reach a constantly increasing minimum level so that eventually the pressure in the demand chamber will be above the atmospheric pressure at the beginning of the inspiration cycle which will cause a transition from the well-known demand type of breathing to the so-called pressure breathing, that is in which the pressure existing within the mask will exceed the ambient atmospheric pressure and may rise to four inches of water or more above the ambient atmospheric pressure. This will force oxygen under positive pressure into the lungs during inspiration and will force the aviator to exhale with a pressure higher than the existing mask pressure. When the pressure breathing transition point is reached the entire area of the diaphragm 62 will be subjected to this pressure which will now be above the atmospheric pressure existing in the chamber 75. In order to overcome the affect of this force the diaphragm will engage the stationary annular stop 65 and only the central portion of the diaphragm in the annular opening 66 will be effective. At this time the aneroid spring 68 will be rendered substantially ineffective and spring 70 will come into action, the aneroid in the meantime having expanded an amount equal to the clearance between the bottom coil of the spring 70 and the abutment disk 69. Spring 70 being a heavier spring will transmit the force from the expanding bellows to the diaphragm 62, and even though the pressure in chamber 60 is above the atmospheric pressure acting in chamber 75 plus the force from the aneroid bellows assembly 76 transmitted by spring 70 will be sufficient to cause the pilot valve 58 to be moved in accordance with the variation in pressure in chamber 60 transmitted from the demand chamber 40 during the inspiration cycle. By means of the stop plate 65 the effective area of the diaphragm is reduced so that it is possible to use a very small diaphragm to accomplish the function that would normally require a much larger diaphragm area. As soon as the pressure within the mask rises above the ambient atmospheric pressure the diluter valves of Figs. and 6, whichever one is employed, will become ineffective and air dilution will cease. The higher the aircraft ascends the greater will be the expansion of the aneroid assembly 76 and the higher will be the mask pressure to insure adequate pressure breathing.

Atany time that there is a malfunction of the regulator the aviator can strike the knob 87, Fig. 4, with his hand and against the resistance of the coil spring 88 cause the entire aneroid assembly to move downward and through springs 68 and 70 and cause the pilot valve 58 to move wide open causing an immediate follow-up on the main valve 43 to permit a full flow of oxygen from the inlet 47 and inlet chamber 45 into the demand chamber 40. The aviator by alternate operation of the knob 87 can thus get any desired amount of oxygen admitted to the mask dur ing inspiration that he desires irrespective of altitude conditions. Obviously if regulator malfunction continues the aviator would immediately descend to a safe lower altitude where he could get air from the ambient atmosphere through the diluter valve 95, Fig. 5, or 106, Fig. 6.

In the event of oxygen failure the diluter valve, Fig. 6 when employed in the mask such as shown in Fig. 2 will cause an increased breathing restriction against inflow of atmospheric air through the diluter valve 106 warning the aviator to immediately descend as specifically described above with respect to the description of the valve, Fig. 6.

In the regulator as described with respect to Fig. 4 control springs have been employed to return valves to their neutral position. It should be understood that in the case of the main valve sufficient resilience may be employed in the diagram to eliminate the necessity of the spring and the exhalation valve could also be yieldingly mounted eliminating the need of a coil spring.

Variations, changes and modifications will be apparent to those skilled in the art. Accordingly I do not wish my invention to be limited other than as expressed in the appended claims.

I claim:

1. In an oxygen breathing system of the character described, a housing having an oxygen inlet and an outlet, a main valve controlling oxygen flow from said inlet to said outlet, fluid pressure motor means for actuating said main valve, said motor means utilizing inlet oxygen as a working fluid and discharging the same to the outlet, 2 pilot valve controlling said motor means, a diaphragm in said housing adapted to actuate said pilot valve, said diaphragm being subject on one side thereof to atmospheric pressure and on the opposite side to delivery pressure and movable in response to the difference in such pressures, an aneroid bellows subject to atmospheric pressure for applying a loading force on said diaphragm and pilot valve, and an annular stop in said housing positioned so as to be contacted by said diaphragm when the delivery pressure minimum level exceeds the ambient atmospheric pressure, said stop reducing the effective area of said diaphragm opposing the loading imposed thereon by said aneroid.

2. In a high altitude pressure-demand breathing system for aviators a regulator adapted to be mounted on the forward wall of an oxygen mask comprising a small cylindrical housing having its inner end open and communicating with the mask interior to form an oxygen outlet, an oxygen inlet to said housing, means including a demand chamber and a primary valve establishing a flow path between said inlet and said outlet, said primary valve determining the pressure and quantity of oxygen delivered to said outlet, means defining a secondary flow path between said inlet and said outlet including a pressure responsive expansible chamber for actuating said primary valve and a pilot valve for controlling the flow and thereby the pressure in said secondary flow path to vary the pressure in said pressure responsive expansible chamber, a chamber connected to said demand chamber and having a flexible wall and subject on one side to atmospheric pressure and on the other side to chamber pressure, said flexible wall being operatively connected to the pilot valve to actuate the same, an evacuated aneroid acting on said flexible wall in opposition to chamber pressure and an annular stop adapted to engage said flexible wall when chamber pressure exceeds the ambient atmospheric pressure, said aneroid being operative to exert its control bias against the central portion of the flexible wall not engaged by said annular stop.

3. The structure as claimed in claim 2 in which the aneroid and the flexible wall member have a pair of concentric springs interposed therebetween for transmission of force from the aneroid to the flexible wall by compression of the springs one of said springs being shorter in length than the other spring whereby it remains out of action until the deflection of the aneroid exceeds a predetermined amount.

4. The structure as claimed in claim 2 in which the means for transmitting the biasing force from the aneroid to the flexible wall includes spring means in which the efiective stiffness increases when the aneroid has expanded beyond a predetermined amount.

5. In a high altitude oxygen breathing system, a mask adapted to be positioned on the wearers face, a source of oxygen under pressure, a small cylindrical housing having an open end mounted on the forward wall of said mask with the open end forming an inhalation and exhalation passage communicating with the interior of the mask, exhalation ports in said housing communicating with the atmosphere exterior to the mask and an exhalation valve within said housing responsive to pressure within the mask for connecting said exhalation ports with said inhalation-exhalation passage, an oxygen delivery chamber in said housing and a flapper type inhalation valve controlling flow of oxygen from said delivery chamber to said inhalation-exhalation passage, a demand regulator positioned in said housing forward of said oxygen receiving chamber, said regulator including an oxygen receiving chamber connected to said oxygen source, a port interconnecting said oxygen receiving and delivery chambers and provided with a valve seat, a diaphragm cooperating with said valve seat to form a valve controlling flow through said last-named port, said diaphragm forming one wall of a control chamber, a restricted flow connection between said oxygen receiving chamber and said control chamber, a pilot valve for venting pressure from said control chamber to said oxygen receiving chamber, a second diaphragm, responsive to inhalation for actuating the pilot valve to cause operation of the diaphragm valve proportional to the difference in pressure on opposite sides thereof, an aneroid positioned at the outer end of said housing adapted to exert a biasing force on said second diaphragm in response to ambient atmospheric pressure above a certain altitude and manual means accessible from the front of said housing for directly actuating said pilot valve to cause said diaphragm valve to open to a maximum extent irrespective of altitude.

6. In a high altitude oxygen breathing system, an oxygen mask, a source of oxygen under pressure, a small casing having an open end mounted on the forward wall of said mask with the open end communicating with the interior of the mask and said housing extending forward from the mask wall, a pressure demand regulator positioned in the forward portion of said housing, a connection between said regulator and said oxygen source, an inhalation-exhalation valve positioned within the open end of said housing and permitting inhalation of oxygen from said regulator and exhalation therethrough, exhalation ports controlled by said exhalation valve, said exhalation ports extending circumferentially through said housing and a cylindrical extension of the front wall of said mask concentric with and spaced from the exterior of the housing to form an annular passage communicating at one end with said exhalation ports and at the other end with the ambient atmosphere whereby the warm exhaled air is in contact with said housing substantially throughout its length.

7. In an oxygen breathing system including an oxygen mask, a small cylindrical housing mounted on and projecting forwardly from the front wall of the mask, said housing having its inner end open and communicating with the interior of the mask, means forming an annular valve seat within said housing adjacent its open end, radial exhalation ports in said housing adjacent said valve seat, a disc valve cooperating with said annular valve seat such that when open, said housing open end is in direct communication with the exhalation ports, an inhalation valve centrally disposed on said exhalation disc valve and operative to permit oxygen flow from a demand chamber in said housing to the mask, an oxygen inlet in said housing, means establishing a primary flow path from said inlet to said outlet including a pressure reducing valve, means establishing a secondary flow path from said inlet to said demand chamber including a double acting pressure responsive motor means for actuating said pressure reducing valve, a pilot valve for controlling flow in said secondary flow path for thereby controlling said motor means, a diaphragm subject on one side to atmospheric pressure and on the other side to the pressure in said demand chamber for actuating said pilot valve, a stop for limiting the effective area of said diaphragm subject to demand pressure, an aneroid for applying a biasing force to said diaphragm and pilot valve as a fiunction of altitude, a pair of parallel acting springs for transferring force from said aneroid to said diaphragm one of said springs remaining inactive until a predetermined pressure altitude has been reached.

8. The structure as claimed in claim 6, in which means including a flapper valve form a bypass for flow of diluter air to the mask so long as mask pressure is less than ambient atmospheric pressure, means for restricting the inlet of dilution air to said valve, a bellows adapted when expanded to render said restricting means inoperative and a connection between the oxygen inlet in said housing and said bellows to expand the same so long as an oxygen supply is available, collapse of said bellows due to drop in oxygen pressure causing a high resistance to inspiration of air through the diluter valve so as to warn of the oxygen supply failure.

9. In an automatic regulator of the class described having an oxygen inlet and an oxygen outlet with a pressure regulating main valve interposed in the path of flow from the inlet to the outlet and pilot valve controlled servo mechanism for actuating said main valve and having a diaphragm subjected to atmospheric pressure on one side and to pressure in said outlet on the opposite side, said diaphragm being operative to actuate said pilot valve in accordance to the difference in pressure acting thereon, the improvement which consists of an aneroid bellows subject to atmospheric pressure, a pair of concentric springs for transferring force from said aneroid to said diaphragm, an annular stop positioned above said diaphragm and adapted to contact the same when outlet pressure acting thereon exceeds atmospheric pressure, the outer spring of said pair of springs engaging said diaphragm adjacent the interior marginal edge of said annular stop, the other spring of said pair of springs being adapted to contact said diaphragm radially inward of the outer spring, the inner spring being shorter in length than the outer spring and adapted to engage the diaphragm only when the aneroid has expanded beyond a predetermined amount.

10. A diluter valve for an oxygen mask of the character described including a hollow casing adapted to be mounted through the oxygen mask wall, ports connecting the interior of said casing at one end to the atmosphere, inlet ports at the other end of the casing adapted to connect the interior of the casing to the interior of the oxygen mask, an outwardly opening flapper type valve controlling said last named ports, a transverse partition in said casing, ports in said partition wall, a disc valve covering said partition ports and movable in the same direction as said flapper valve to open said ports, a bellows in said casing, a connection between said disc valve and said bellows,

References Cited in the file of this patent UNITED STATES PATENTS Meidenbauer Nov. 2, 1948 Seeler May 13, 1952 Hull et a1 June 21, 1955 Holmes Nov. 26, 1957 

